Who was the first ruler of Delhi Sultanate?

The correct answer is Option (3) → Qutub-U-Din-Aibak

Qutb-ud-din Aibak, a Turkish slave who rose to be a general of Muhammad Ghori, took charge of Ghori’s conquests in India after Ghori’s death in 1206. He thus became the first ruler of the Delhi Sultanate and founded the Mamluk (Slave) dynasty. He began building the Qutb Minar in Delhi and died in 1210 after a fall from his horse while playing polo. His son-in-law Iltutmish, who came to the throne in 1211, made the Sultanate secure.